Production of o-nitrochlorbenzol-p-sulfonic acid



Patented Feb. 5, 1929.

'UNITEDSTATES PATENT OFFICE.

HOMER W. HILLYER, OI FABHINGTON, CONNECTICUT, ASSIGNOR TO NATIONAL ANI- LINE & CHEMICAL COMPANY, INC., OF NEW YORK, N. Y., A. CORPORATION OF NEW YORK.

PRODUCTION OF O-NITBOCKLORBENZOL-P SULFONIC A OID.

R Drawing.

This invention relates to improvements in the production of the alkali metal salt of o-nitrochlorbenzol-p-sulfonic acid from chlorbenzol.

According to the present invention, the chlorbenzol is sulfonated to convert it into the chlorbenzol-p-sulfonic acid. The sulfonic acid so produced is subjected to n1- tration, while still in admixture with the excess sulfuric acid from the sulfonation, by the addition of mixed acid (mixed sulfuric and nitric acids) or of sodium nitrate, and the o-nitrochlorbenzol-p-sulfonic acid so formed is isolated and recovered from the n1- tration product in the form of its sodium salt. The invention includes certain improvements in the sulfonation, nitration and isolation operations, aswell as in the comb1'- nation of these operations, all as more fully hereinafter set forth and as claimed.

The-sulfonation and nitration operations can be advantageously carried out the same vessel, e. g., in a large cast iron or wrought iron kettle, the excess sulfuric acid from the sulfonation remaining present and assisting in the nitration, and the nitration mixture being then diluted b pouring it into water in awooden vat, an the sulfonated and nitrated product then isolated from the diluted mixture by salting out, accordin to any one of the methods hereafter descri ed, so that the product is obtained in the form of its sodium-salt.

' :The sulfonation of the chlorbenzol can be efiected to advantage with 100% sulfuric acid. Instead of 100%-acid, however, oleum, or. a mixture of common and fuming acid, or a mixture of 100% acid and fuming-acid, can be used. For example, an amount of oleum can be used such that the sulfuric acid remainin when the sulfonation is com leted will still be-as strong as 100% acid. leum 5 containing up to 26% S0 has been used, but it is unnecessary to use an acid of such strength, audit is entirely feasible to obtain satisfactory results with 100% acid. A suitable xcess of the sulfonating acid is used, to

insure completion or substantial completion of thesulfonation, and this excess will accordingly'be; present in admixture with the sulfo'nic-acid, at the end of thesulfonation.

' It is not-necessary to -isolate the chlor-ben- 'zol-sulfonicflacid from the excess sulfuric I I acid, but this excess acid is made use of in Application filed January 30, 1920. Serial No. 355,157.

the subsequent nitration, thereby contributmg to both the sulfonation and nitration operations as well as to the isolation of the sodlum salt of the o-nitrochlorbenzol-p-sulfonic acid.

The nitrationof the chlorbenzol-sulfonic acid is effected by adding either mixed acid (sulfuric and nitric) or sodium nitrate to the sulfonatlon mixture, and maintaining a regulated temperature of about 30 to C. during the nitration. Somewhat higher and lower temperatures can be used, but if the temperature is too low the nitration takes place too slowly, while if too high, decomposltion tends to take place and a less pure prodnot is formed. The amount of mixed acid, or of sodium nitrate, may vary somewhat, since a considerable excess of nitric acid does no particular harm, and di-nitration, does not eas1ly take place. A large excess of nitric acid is not, however, necessar and should ordinarily be avoided. That is, the process can advantageously be carried out with an amount of the nitrating agent that does not greatly exceed thetheoretical, and the process can readily be carried out without ob'ectionable over-oxidation. So also, the nitrating agent added, i. e.,'sodium nitrate or nitric acid or mixed acids does not remove the sulfuric acid by converting it into the form of an insoluble precipitate, but leaves the sulfate radical in solution. 0

The process of nitration in which sodium nitrate is used and added to the product of the sulfonation has, among others, the ad vantage that subsequent salting out of the nitrochlorbenzol-sulfonic acid as the sodium salt is promoted by the sodium of the sodium nitrate, so that less added salt will herequired.

At the end of the nitration, the nitration product is diluted with waterand the nitrochlorbenzol-sulfonic acid is separated as the sodium salt. The nitration product will still contam the excess sulfuric acid from ,thesulfonation, (except for such amounts as have combined with the sodium nitrate to a set free nitric acid and form sodium sulfate,

in the sodium nitrate process of nitration), j as well as any excess of nitric acid, and it is to separate the nitro-= is excess acid in order; p to obtain it in an isolated state. This isola-' tion and recovery is effected, according to the accordingly neces'sar sulfonic acid from-til present invention, by converting the sulfonic acid into its sodium salt, and separating this sodium salt in a solid state, by the addition of common salt to dilute solutions.

This separation of the nitrochlorbenzolsulionic acid as its sodium salt can be effected in one or another of the following procedures: (1), Common salt (sodium chlorid) 1s added to the diluted nitration mixture in the same vat in which the dilution is effected, so that the sodium salt of the sulfonic acid is separated from the still acid solution; (2), the excess sulfuric acid as well as the free i, sulfonic acid, is neutralized with lime (or its equivalent) and thereby converted into calcium sulfate and calcium sulfonate, the calcium sulfate is filtered oil, the calcium sulfofected as in nate in solution is converted into the sodium sulfonate by adding sodium carbonate, with formation of calcium carbonate which is filtered OE, and the sodium sulfonate is then separated from its solution by the addition of common salt; (3), neutralization is of- (2) the calcium sulfate is filtered off, and common salt is then added to the calcium sulfonate solution to convert the calcium sulphonate into sodium sulfonate and to separate the sodium sulfonate in a solid state, such that it can be filtered oii'. Of these alternative methods of isolating the o-nitrochlorbenzol-p-sulfonic acid as its sodium salt, the first method has the disadvantage of requiring the filtration of the still acid liquor, in order to obtain the separated sodium salt therefrom, but it has the advantage of not requiring neutralization with lime and filtration of calcium sulfate or gypsum, and it can be carried out in the same vat used for dilution of the nitration roduct. The second and third methods avoi the filtration of acid liquors. In so far as I am aware, it is broadly new to effect the separation and recovery of the o-nitrochlorbenzolp-sulfonic acid from the product of sulfonation and nitration which results in its production, as the sodium salt, by any of the procedures above described. In addition, the third method of isolation is, as I believe, an entirely new method of isolation, not only as applied to the isolation of this particular sulfonic acid from the sulfonation and nitration product, but also as applied to the separation and recovery of sulfonic acids generally from the excess sulfuric acid used in their sulfonation. I have accordingly made this third method of separation, when practiced in connection with the production and isolation of the o-nitrochlorbenzol-p-sulfonic acid, as well as covery of sulfonic acids as their alkali salts, the subject-matter of a separate application for patent, Serial No. 349,239, filed January 3, 1920, which has matured into Patent No.

- The invention will be further illustrated applied generally to the reby the following specific examples, the parts being by weight:

Sulfonation of chl0rbenz0l.-100 parts of chlorbenzol are mixed with about 265 parts of 100% sulfuric acid in a jacketed iron kettle provided with means for cooling and steam heating. The mixture is heated gradually to 90 C. while actively stirring, and kept at 90 to 100 C. until the odor of chlorbenzol disappears or is only faintly perceptible. The chlor-benzoLp-sulfonic acid thus produced need not be isolated from the sulfonation product, but can be subjected to nitration in the same kettle, and While still in admixture with the excess sulfuric acid from the sulfonation.

Nitration of cklorbenzoLp-sulfonic acid using mixed acid.The sulfonation mixture, produced as above described, is cooled to about 20% O. and about 193 parts of mixed acid (containing about 29% HNO 65% H SO, and 6% water) are gradually run in, with stirring, the temperature being kept between 30 to 50 C. The stirring is continued for some time after tendency to spontaneous heating ceases, to insure completion or substantial completion of the nitration, and the product is then run into about 1800 parts of water, with stirring.

Nitration 0f ehlorbenzol-p-sulfonio acid, using sodium nitrate.The sulfonation mixture, produced as abovedescribed, is cooled to about 20 0., and 80 parts of finely ground sodium nitrate are slowly sifted in, with vigorous agitation, at, such a rate as to keep the temperature between 30 and 50 C. The time required will vary somewhat, depending upon the cooling eflect obtainable, the amount of the mixture treated, etc., but may require as much as two hours or more. The mixture is stirred for a further period of about twelve hours, while keeping the temperature at 30 to 50 (1, and it is then run into about 1800 parts of water, with stirring.

Isolation of o-nitrocklorbenzoZ-p-sulfoni0 acid as sodium salt.

Example 1.To the acid solution, produced in accordance with either of the above examples by diluting the nitration products with water, there is added 350 parts of common salt, and the mixture is stirred until the granular precipitate of the sodium salt which soon forms breaks up into smaller crystals glving a pasty mass. The mixture is then cooled until the temperature falls to about 15 (3., filtered to separate the sodium sulfonate, and the sulfonate washed with a 15% salt solution. The sodium salt of the o-nitrochlorbenzol-p-sulfonic acid is thus obtained in an isolated state.

Example 2.The acid solution is cooled to 30 C. or below and milk of lime is slowly added at such a rate that the temperature does not rise above 40 C. until neutrality is reached, but avoiding excess of lime. The excess sulfurlc acid is neutrahzed and separated as calcium sulfate or gypsum, .while the and the press cake washed with hot water :The calcium sulfate is thus removed, leaving the calcium sulfonate in solution. About 40 parts of sodium carbonate are added to the calcium salt solution, while heated to boiling, thereby changing the calcium salt into the sodium salt (of the nitrochlorbenzol-sulfonic acid) and precipitating the calcium as calcium carbonate, which is filtered off, leaving the sodium salt in solution. To this solution there is added about 1 part of common salt for each six parts of the solution, and the solution is stirred while cooling to about 15 C. The sodium salt is thus precipitated and is filtered oif, the press cake washed with 15% brine, and sucked or blown dry, thus isolating the, o-nitrochlerbenzol-p-sulionic acid in the form of its sodium salt.

Example 3.To the calcium sulfonate solution, obtained as described in Example 2, by neutralization and filtration, there is added about 1 part of common salt for each 6 parts of the solution, and the resulting mixture is stirred and cooled to about 15 C. The common salt sodium chlorid) thus added reacts withthe calcium sulfonate in solution, by double decomposition, to form the sodium sulfonate, which is precipitated in a solid form, as more fully described in my said companion application, Serial No. 349,239. The sodium salt of the o-nitrochlorbenzol-p-sultonic acid thus produced. and separated is filtered off and the press cake washedwith brine, thus giving the sodium salt in an isolated state. i

If sodium nitrate is used for the nitration operation, the subsequent separation of the sodium sulfonate from the dilute solutions is thereby promoted, inasmuch as the sodium of the sodium nitrate remains as sodium salts, thus increasing the sodium content of the solution when the common salt is added, and promoting the formation and separation of the sodium sulfonate, or permitting the use of somewhat decreased amounts of common salt for the precipitation of the sodium sulfonate.

The sodium salt of the o-nitrochlorbenzolp-sulfonic acid obtained as above described is admixed with va ing amounts of common salt, but it is of su cient purity for further treatment or use, for example, in the production of o-nitrophenol-p-sulfonic acid and oaminophenol-p-sulfonic acid. The sodium salt can be dried, and thus obtained in a dried and isolated state, or it can be further purified, where a product of greater purity is required.

I do not claim specifically herein the method of producing and isolatlng the nitrochlorbenzoI-sulfonic acid in the form of its sodium salt, which includes the formation of calcium salt solutions and the treatment of such solutions with common salt to effect the conversion of the calcium sulfonate into sodium sulfonate, and the separation of the sodium sulfonate by the same operation, (the third method of isolation described above), inasmuch as such process is described and claimed in my said companion application, Serial No. 349,239. The claims of the present case are intended to be of a more general or generic character, in so far as they include such method of production and isolation, while the more specific claims of the present case are directed to a different specific method of pro duction and isolation.

I claim:

1. In the process of producing o-nitrochlorbenzol-p-sulfonic acid by treating chlorbenzol-p-sulfonic acid with a nitrating agent in the presence of sulfuric acid, the improvements which comprise using in the processa weight of nitrating agent substantially equal to that theoretically required and carrying out the process of nitration at a temperature of about 3050 C;

2. In the process of producing o-nitrochlorbenzol-p-sulfonic acid by subjecting chlorbenzol-p-sulfonic acid to the action of a nitrating agent in the presence of sulfuric acid, the improvement which comprises using in the process-a weight of nitrating agent substantially equal to that theoretically required.

3. The method of producing o-nitrochlorbenzol-p-sulfonic acid which comprises adding a nitrating agent in an amount that does not greatly exceed the theoretical to the product of sulfonation of chlorbenzol, the nitrating agent being of such a character that it does not remove the sulfate radical from the solution, and carrying out the nitrating operation while maintaining a regulated temperature of about 30 to 50 C.

54. The improvement in the sulfonation of chlorbenzol which comprises subjecting the chlorbenzol to sulfonation by mixing about 100 parts of chlorbenzol with about 265 parts of 100% sulfuric acid and keeping the temperature at about 90 to 100 C. until the sulfonation is efiected.

In testimony whereof I afiix my signature.

HOMER W. HILLYER. 

